#include "gzip.h"
#include "zlib.h"

/* Compress gzip data */
/* data 原数据 ndata 原数据长度 zdata 压缩后数据 nzdata 压缩后长度 */
int gzcompress(Bytef *data, uLong ndata, Bytef *zdata, uLong *nzdata)
{
    z_stream c_stream;
    int err = 0;

    if (data && ndata > 0)
    {
        c_stream.zalloc = NULL;
        c_stream.zfree = NULL;
        c_stream.opaque = NULL;
        //只有设置为MAX_WBITS + 16才能在在压缩文本中带header和trailer
        if (deflateInit2(&c_stream, Z_DEFAULT_COMPRESSION, Z_DEFLATED,
                         MAX_WBITS + 16, 8, Z_DEFAULT_STRATEGY) != Z_OK)
            return -1;
        c_stream.next_in = data;
        c_stream.avail_in = ndata;
        c_stream.next_out = zdata;
        c_stream.avail_out = *nzdata;
        while (c_stream.avail_in != 0 && c_stream.total_out < *nzdata)
        {
            if (deflate(&c_stream, Z_NO_FLUSH) != Z_OK)
                return -1;
        }
        if (c_stream.avail_in != 0)
            return c_stream.avail_in;
        for (;;)
        {
            if ((err = deflate(&c_stream, Z_FINISH)) == Z_STREAM_END)
                break;
            if (err != Z_OK)
                return -1;
        }
        if (deflateEnd(&c_stream) != Z_OK)
            return -1;
        *nzdata = c_stream.total_out;
        return 0;
    }
    return -1;
}

/* Uncompress gzip data */
/* zdata 数据 nzdata 原数据长度 data 解压后数据 ndata 解压后长度 */
int gzdecompress(Byte *zdata, uLong nzdata, Byte *data, uLong *ndata)
{
    int err = 0;
    z_stream d_stream = {0}; /* decompression stream */
    static char dummy_head[2] = {
        0x8 + 0x7 * 0x10,
        (((0x8 + 0x7 * 0x10) * 0x100 + 30) / 31 * 31) & 0xFF,
    };
    d_stream.zalloc = NULL;
    d_stream.zfree = NULL;
    d_stream.opaque = NULL;
    d_stream.next_in = zdata;
    d_stream.avail_in = 0;
    d_stream.next_out = data;
    //只有设置为MAX_WBITS + 16才能在解压带header和trailer的文本
    if (inflateInit2(&d_stream, MAX_WBITS + 16) != Z_OK)
        return -1;
    // if(inflateInit2(&d_stream, 47) != Z_OK) return -1;
    while (d_stream.total_out < *ndata && d_stream.total_in < nzdata)
    {
        d_stream.avail_in = d_stream.avail_out = 1; /* force small buffers */
        if ((err = inflate(&d_stream, Z_NO_FLUSH)) == Z_STREAM_END)
            break;
        if (err != Z_OK)
        {
            if (err == Z_DATA_ERROR)
            {
                d_stream.next_in = (Bytef *)dummy_head;
                d_stream.avail_in = sizeof(dummy_head);
                if ((err = inflate(&d_stream, Z_NO_FLUSH)) != Z_OK)
                {
                    return -1;
                }
            }
            else
                return -1;
        }
    }
    if (inflateEnd(&d_stream) != Z_OK)
        return -1;
    *ndata = d_stream.total_out;
    return 0;
}
